Saturday, August 16, 2014

July Was Hot and Cold

For some reason, I've always been fascinated with the climate record for July. Perhaps it's because it is the hottest month of the year at most (but not all) locations. This year was particularly interesting.

Let's start in Utah. As we've discussed previously (see Near or Above Average Temperatures Are an Easy Bet in July), you can usually count on above average temperatures in July in Utah, and this year didn't disappoint. On a statewide basis, the average temperature was 75.5ºF, 3.0ºF above average and the 7th warmest July on record. The last July with a statewide mean temperature below the 20th century average was 1997.

Source: NCDC

At the Salt Lake city International Airport, we only had two days with a temperature above 100ºF (July 14 and 23rd, both of which hit 103ºF), and we had a really nice cool down during a big monsoon surge at the end of the month (high temperatures of 76, 82, and 85ºF on July 29, 30, and 31, respectively). Nevertheless, sustained high temperatures for most of the month gave us a mean temperature of 81.9ºF, 4.4ºF above the 1948–2000 average and the 6th warmest July since records at the airport began in 1948.

Source: NCDC

We've discussed previously that the apparent cooler temperatures this July compared to last July is at least partly a result of a high temperature sensor bias at the airport last summer (see Was July 2014 Cooler Than July 2013) and indeed when one looks the average temperature for the North Central Utah Climate Zone, which encapsulates the Wasatch Front, one finds that the mean July temperature for this summer was just 0.4ºF cooler than last summer. In addition, although last summer was hot, for this climate region, 2002, 2003, 2006, and 2007, were clearly hotter. Nevertheless, both summers were clearly well above the 20th century average.

Source: NCDC

Nationally, July was really interesting, with persistent ridging over the Pacific Northwest and troughing over the upper midwest leading to record high temperatures over the former and record cool temperatures over the latter. Temperatures along the Oregon and northern California coastal zone were the highest on record, whereas they were the coolest on record from Arkansas to southern Lake Michigan. Most of the west saw above average (in some cases well above average) temperatures), whereas much of the midwest saw below average (in some cases well below average) temperatures.

It must have been a remarkably pleasant July (by climatological standards) in the midwest.

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The Wasatch Weather Weenies discuss the weather and climate of the Wasatch Front and Mountains, western United States, and beyond.

Participants include aspiring and old-school atmospheric scientists, weather enthusiasts, powder snobs, and poor souls enrolled in classes taught by University of Utah Atmospheric Sciences Professor Jim Steenburgh. Many posts feature content or insights enabled by the support of the National Science Foundation, Office of Naval Research, and the NOAA/National Weather Service.

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